1. Field of the Invention
This invention relates to a thickening system for cleaning products comprising a surfactant, a fluorescent whitening agent or dye and a pH adjusting agent, and more particularly to a liquid oxidant bleach laundry composition thickened with such a system.
2. Description of the Prior Art
Much prior art has addressed the development of thickened household laundry products such as detergents or bleaches. Consumer preference for such thickened products is well documented, and applications include prewash products or hard surface cleaners which require concentrating the active ingredients and/or the capability to cling to surfaces. Typical thickeners of the prior art include surfactants, polymers, or combinations of polymers and surfactants. Various disadvantages are associated with such prior art thickening systems. To the extent that a thickened laundry product requires the addition of components solely for thickening, the cost of the product is increased. Many prior art thickeners are incompatible with oxidizing species, e.g., bleaches.
Liquid bleaches have been known and used in a variety of household applications for a great many years. Chlorine bleaches are used extensively since they are highly effective, inexpensive, and simple to produce. In certain applications, however, non-chlorine, e.g. peroxygen or peracid bleaches are preferred. For maximum effect, non-chlorine bleaches should contain surfactants for detergency, fluorescent whiteners or optical brighteners to increase fabric reflectance, and dyes for producing a pleasing color. Peroxide bleaching compositions of the prior art have not been commercially successful due to problems with stability of the composition when formulated with such additives.
Prior art efforts to develop peroxide laundry products include compositions described in U.S. Pat. No. 4,430,236 issued to Franks, which describes peroxide combined with a detergent-effective amount of a nonionic surfactant, and a fluorescent whitening agent. Franks also discloses the use of a chelating agent in an effort to stabilize the hydrogen peroxide bleach, and the use of a solvent to reduce the viscosity of the composition. U.S. Pat. No. 4,448,705 issued to Grey describes a peroxy bleach with a chelating agent, a bleach activator such as a polyacylated amine, anionic, nonionic, zwitterionic, or cationic surfactants, and may include optical brighteners. Barrett, U.S. Pat. No. 3,970,575 describes a peroxide bleach with a nonionic surfactant and phthalocyanine blue dye. Krezanoski, U.S. Pat. No. 3,852,210 describes a peroxygen containing concentrate formulated with a polyoxypropylene copolymer, a betaine surfactant, and an acid or base to adjust the pH. The formulation may also include a chelating agent, and is primarily intended for germicidal use, although fabric bleaching is mentioned. U.S. Pat. No. 4,347,149 issued to Smith et al describes a detergent composition of hydrogen peroxide, ethanol plus amino compounds as stabilizers, phosphonate compounds, and anionic, nonionic, or amphoteric surfactants. U.S. Pat. No. 4,525,291 also issued to Smith et al describes peroxide-containing compounds including a builder, anionic or nonionic surfactants and alkyl metal aryl hydrotropes for phase stability, and can include optical brighteners. Goffinet et al, U.S. Pat. No. 4,470,919 discloses a hydrogen peroxide bleach composition incorporating a surfactant and a fatty acid. Lutz et al, U.S. Pat. No. 4,130,501 describes a viscous peroxide bleach containing from 0.5 to 4% of an anionic or nonionic surfactant and thickened with a copolymer of carboxylic acid with a polyol. No optical brighteners are included in the formulations of Lutz et al. U.S. Pat. No. 4,526,700 issued to Hensley et al discloses an unthickened formulation having a fluorescent whitening agent of the stilbene type formed into fibrous particles by coprecipitating the whitener with a sulfonate surfactant in aqueous hypochlorite at a basic pH. Neiditch et al, U.S. Pat. No. 4,497,718, and 4,562,002 describe a viscous fabric softening composition containing a cationic surfactant, a stilbene fluorescent whitening agent and a non-ionizable base. Robinson et al, U.S. Pat. No. 3,655,566 describes a nonthickened bleaching composition including fluorescent whitening agents and anionic or nonionic surfactants, and having a pH above about 10. Claussen et al, U.S. Pat. No. 3,767,587 shows a nonthickened aqueous dispersion of fluorescent whitening agents and anionic, cationic or amphoteric surfactants. Eckhardt et al, U.S. Pat. No. 4,311,605 discloses an unthickened laundry composition including fluorescent whitening agents and surfactants. Thompson, U.S. Pat. No. 4,216,111 shows a colloidal suspension of high levels of fluorescent whitening agent by flocculating the fluorescent whitening agent with an acid, then deflocculating by basification. Becker, U.S. Pat. No. 4,265,631 describes a stable aqueous suspension of high levels of fluorescent whitening agent or dye with an aminoplast precondensate and a nonionic copolymer. Clark et al, U.S. Pat. No. 3,904,544 and 3,912,115 are exemplary of art teaching thickened suspensions of fluorescent whitening agents. These references both teach preparation of a thixotropic slurry containing high levels of a fluorescent whitening agent with a surfactant. Thickening appears to occur due to the high solids content.
Generally, the art showing thickened compositions including fluorescent whitening agents teaches thickening by a high solids (fluorescent whitening agent) content, or by including additional components, e.g., polymers, to achieve the thickening. Aqueous suspensions of fluorescent whitening agents of the art are generally not at acidic pHs.